FIX: Update() Fails to Write Changed Text Field

   recordset.Edit();
   recordset.Field1String="SomeText";
   recordset.Update();
				

  case CFieldExchange::MarkForUpdate:
        {
            if (value.IsEmpty())
                pFX->m_prs->SetFieldFlags(nField,
                    AFX_SQL_FIELD_FLAG_NULL, pFX->m_nFieldType);
            else
                pFX->m_prs->ClearFieldFlags(nField,
                    AFX_SQL_FIELD_FLAG_NULL, pFX->m_nFieldType);
            ...
				

RESOLUTION

If you use a CRecordView for retrieving data, you won't notice the bug because a CRecordView sets or resets a field's null flag depending on whether a user has entered text into the edit control representing that field. The DDX_FieldText() function does the work of setting the field's null flag.

For example, in the AfxFieldText() function, which gets called from the DDX_FieldText() functions, you'll see this code:

*****
BOOL AFXAPI AfxFieldText(CDataExchange* pDX, int nIDC, void* pv,
    CRecordset* pRecordset)
{
    ASSERT_VALID(pRecordset);

    HWND hWndCtrl = pDX->PrepareEditCtrl(nIDC);
    char szT[2];
    if (pDX->m_bSaveAndValidate)
    {
        ::GetWindowText(hWndCtrl, szT, sizeof(szT));
        if (szT[0] == '\0')
        {
            if (pRecordset->IsFieldNullable(pv))
            {
                pRecordset->SetFieldNull(pv);
                return TRUE;
            }
        }
        else
            pRecordset->SetFieldNull(pv, FALSE);
    }
    else
    {
        if (!pRecordset->IsOpen() || pRecordset->IsFieldNull(pv))
        {
            szT[0] = '\0';
            AfxSetWindowText(hWndCtrl, szT);
            return TRUE;
        }
    }
    return FALSE;
}
*****
				

You can see how the null flag for the field is set or reset. You can write similar code to handle setting or resetting the null flag in your code.

As an alternative, you can create a new RFX function, and insert the code shown above for the MarkForUpdate operation. Replace the call to RFX_Text() in your CRecordset's DoFieldExchange() function with your new RFX function.